Recap of Friday and Introduction of Saturday Program (Patricia Lundberg).Presenter: Paula Findlen (History, Stanford University).In 1609 an Italian mathematics professor, Galileo Galilei, devised a telescope based on reports of a spyglass that could magnify things at a distance. He turned it on the heavens and saw things no one had ever seen before: the imperfections of the moon's surface, the composition of the Milky Way, and the hitherto unknown satellites of Jupiter. Galileo's report of these discoveries, the Sidereal Messenger (1610), became a landmark publication in the history of astronomy and made him one of the most important and ultimately controversial astronomers of his time. How did Galileo and his instrument change astronomy? What is the significance of his accomplishment at the distance of 400 years?